1. Origin of the Invention
The invention described herein was made in the performance of work under a NASA contract, and is subject to the provisions of Public Law 96-517 (35 USC 202) in which the Contractor has elected to retain title.
2. Technical Field
The invention relates to active and passive devices for detecting millimeter wave radiation, and particularly to the integration of GaAs semiconductor devices including Schottky diodes and transistors with passive millimeter wave devices such as microstrip circuits, planar antennas and the like.
3. Background Art
At millimeter and submillimeter wavelengths, the mechanical, thermal and dielectric properties of fused or crystalline quartz are ideal for its use as a circuit substrate material. High frequency applications for quartz include many forms of integrated stripline circuits, antenna substrates and dielectric lenses. When scaling such devices for radiation wavelengths less than one micron, many discrete circuit elements become untenably small, making handling and fabrication quite difficult. When, in addition, it is desired to add prefabricated high speed GaAs active devices onto quartz microstrip or antenna circuitry, package size becomes the dominant limitation. Attempting to overcome such a limitation by combining the quartz substrate with the microstrip devices mounted thereon with GaAs substrates prior to fabricating active devices in the GaAs substrates is not possible because there is currently no method for combining or implanting GaAs and quartz prior to device processing.
Thus, it has not seemed practical to integrate GaAs devices with passive microstrip-on-quartz elements for detecting submillimeter wave radiation.
Recently, a technique has been developed for removing or "lifting-off" a very thin (less than 2 micron thick) preprocessed epitaxial layer from the top of a GaAs host wafer and transferring the entire layer to a quartz carrier, as described in E. Yablonovitch et al., "Extreme Selectvivity in the Lift-Off of Epitaxial GaAs Films," Applied Physics Letters, Vol. 51, No. 26, pages 2222-2224, December 1987, and C. Van Hoof et al., "MESFET Lift-Off from GaAs Substrate to Glass Host," Electronic Letters, Vol. 25, No. 2, pages 136-137, Jan. 19, 1989.